Method for producing titanium and zirconium



METHOD FOR PRODUCING TITANIUM- AND ZIRCONIUM Application December 30, 1952 Serial No. 328,789

5 Claims. (Cl. 7584.5)

No Drawing.

This invention relates to the reduction of metals. It relates especially to the reduction of metal halides which can only be reduced with alkali and alkaline earth metals. It has for its object the complete reduction of such metal halides without the presence of an excess of alkali and alkaline earth metal. It also has for its purpose the simultaneous reduction of two or more halides to produce an intimate mixture of finely divided metals.

I have found that a new and highly effective reducing medium for metal halides may be produced by the electrolysis of alkali and alkaline earth metal halides in a compartment cell. The product of my invention is produced in the cathode compartment of such a cell. The structure of the cell and the reaction at the anode are not pertinent to my invention it being suflicient that the cathode product formed at a chemically inert cathode can be removed from the cell without substantial contamination from the-anode product. In my co-pending applications, Serial 152,175, filed Mar. 27, 1950, Serial 256,385, filed Nov. 14, 1951, now Patent No. 2,831,802, issued April 22, 1958, Serial 230,336, filed June 7, 1951 (now abandoned), Serial 277,445, filed Mar. 19, 1952 (now Patent No. 2,783,196, issued February 26, 1957), and Serial No. 326,139, filed Dec. 15, 1952 (now abandoned), of which prior applications the present application is a continuation-in-part. I have disclosed the reaction of the cathode product and the anode product in a cell containing an electrolyte of alkali and alkaline earth metal chlorides and soluble metal anode. I have disclosed in those applications that the cathode product may bring about reduction at some distance ,from the cathode and have identified the cathode product as containing nascent or dissolved alkali and alkaline earth metal and have distinguished such a product from discrete metal formed at the cathode. In my present invention I produce this cathode product and remove it from the cathode compartment of the cell where it can be used for many chemical reactions including the reduction of the anode product in accordance with my co-pending applications. For purposes of discriptionl identify the product of my invention as a solution of a metal selected from the group consisting of alkali and alkaline earth metals in a melt of halides, except fluorides, of said metals. Regardless of this identification of the product of my invention what I produce is a homogeneous melt having high reducing power and forming as the product of reaction with reducible metal halides, finely divided metal and halide of a metal selected from the group consisting of alkali and alkaline earth metals.

The essence of my invention is the production of such a reducing material by the electrolysis in a compartment cell of alkali and alkaline earth metal halides and the removal from the electrolytic zone of the contents of the cathode compartment either continuously or periodically so that no discrete alkali and alkaline earth metal is formed.

The alkali and alkaline earth metal halides used in tates a at the anode.

. 2,922,712 Patented Jan. 26, 1960 my invention must be substantially oxygen-free, and oxidizing gases must be excluded from the operation.

The concentration of reducing material which may be obtained in the melt without the formation of discrete metal depends on the temperature and composition of the salt. in general the alkali metals dissolve in the salt to a greater extent at lower temperatures than the alkaline earth metals, however at high temperatures the alkaline earth metals are more soluble. For example when using a mixture of CaCl and 25% NaCl at 600 degrees C. the metal dissolved is mostly sodium which dissolves up to 5% by weight. With the same melt at 850 degrees C. nearly 20% of metal is dissolved and such metal is mostly calcium.

Since my invention contemplates the use of the cathode product in the condition of its formation, it must be used at the temperature of formation or the concentration developed in the cell must be such that no discrete metal separates when cooling to the temperature of use.

For the reduction of metal halides in accordance with my invention 1 bring the metal halides into solution in molten alkali and alkaline earth halides and mix such solution with the cathode product of my invention. It is desirable to mix the solution of metal halide with the cathode product in such proportions that no excess of either reactant remains after the reactions. Good results can be obtained however by the introduction of metal halides directly when they are relatively insoluble in the alkali and alkaline earth chlorides. For example titanium metal may be formed by the reduction of titanium tetrachloride added to the cathode product. Such a reduction has a great advantage over the use of massive alkali and alkaline earth metal because there is no surface reaction with consequent coating of the surface of the reducing metal and hence incomplete utilization of it.

In certain instances the cathode product of my invention can be utilized for the reduction of insoluble oxides. Such reduction will only proceed until a certain equilibrium value of oxide content in the melt is reached. Consequently to obtain complete reduction it is necessary to treat the oxide with many successive. portions of the cathode product. The oxide must then be removed from the melt after separating the metal. This can be most conveniently done with incandescent carbon. As an example, this procedure permits the complete reduction of titanium dioxide by passing the cathode product thru a bed of titanium dioxide and then thru a bed of incandescent carbon to deoxidize the partially spent cathode product and returning it to the cell for regeneration and reuse.

I have now described the general nature of my invention which encompasses the reduction of titanium group metal halides, other than fluorides, by the single phase product formed at the cathode when electrolyzing halides, other than fluorides, of the alkali and alkaline earth metals in a compartment cell. -1 will now illustrate my invention with several examples:

Example I I take anhydrous oxygen-free calcium chloride and melt it in an atmosphere inert to calcium chloride. I pass this molten salt at 850 degrees C. separately thru the compartments of an H cell, that is, a cell having two compartments connected by a salt bridge. I allow the melt to pass uninterruptedly thru the anode compartment which is provided with a graphite electrode. Provision is made to dispose of the chlorine which forms The salt is removed from the cathode compartment periodically when it has become almost saturated with calcium, this occurs at about 0.2 mole fraction of calcium. This product is mixed with an ox- I take' anhydrous strontium, iodide free from 'oxygen and'p'roceedasin Examp-leIexcept-that Iuse' a temperature of 600 degrees'C., and permit the concentration of strontium in the'catholyte to build up 'to 0.35 mole fraction'before removing .itfrom-t'hecell. The iodine formed at the anode is col'lected'fonreuse. The cathode product is mixed with Til; the latter beingadded in "the liquid form at 3 'degrees 'C. The reaction takes place immediately and-metallic titanium is formed thruout the melt. The salt is separated from the metalby solution in-alcoholpreventingany-possibility'of oxidation "by. reaction with water.

- Example III I take an anhydrous oxygen-free melt of 50% KCland 50% LiCl and use as in Example. I. The temperature is 45.0 deg. .C. and the molten salt ispass ed continuously thru the catholyte chamber which as in previous examples is provided with a .steel. cathode. The rate of passage is such that the concentration of alkali metal in the meltdoe's not-exceed 0.05 mole fraction. The cathode product is mixed with a. solution of ferrous chloride and nickel chloride in equimolecular proportions in the KCl-i-LiCl mixture. .Since these metals do not form lower chlorides it is immaterial which reactant is temporarily in excess so long as the reaction is completed without substantial excess of-either. An extremely: intimate mixture of very fine nickel. and iron powders is formed which is separated from the salt by water solution of the latter. .This mixture of metal powders is especially suited to the preparation of. alloys of the constituents by powder metallurgy methods. 'Such alloys are more uniform and can be formed atlower temperature.

Example IV In this example 'I takecalcium chloride as in the first example but. I'do not-remove :it .from the cathode.:compartment. of the :cell. When the. concentration of calcium. has beenbuilt up..to. 0.15 =.mol fraction 'l stop the electrolysis and add, Zrcl with; stirring. A suitable :condenser .isprovided to. collectthe portion. of .the ZrCl; whichwis 'volatilized. 'Thisportion is-readded. Whenthe calcium has .all been reacted with ZrCl thecathode. compartment of the; cell is drained. and the. zirconiumseparated from thesalt.

In all of the above examples the current densitywas maintained at a value which gave. a potential between the cathode-and the electrolyte of above 2.0 volts. Beyond this requirementv the current-density is not critical.

, What. is. claimed is:

1. Process of producing .in subdivided forma :first group metal selected from the group consistingofzTi and,

Zr from a halide of said first group metal, which comprises preparing a substantially oxygen-free solution of said first group metal halide in a substantially oxygenfree molten halide selected from the group consisting of the chloride, bromide and iodide of a second group metal selected from the-group consisting of alkali and alkaline ea-nthpmetals, separately preparing a .substantially oxygen-free solutiontof .saidsecondgroup metal in a melt consisting essentially of at least one halide selected from thegroup consisting of the ohloridepbromide and iodide of said second group metal, and then effecting a reaction between said solutions exclusively by'bring'ing said solutions; together. in an environment. ifree from oxidizing gases and underasuc'h conditions that in the zone of reaction there is no excess of either reactant over the stoichiometr'ic equivalent for reaction to form said first group metal.

2. v'Ihe process.- defined in. claim .1, in which the solution. of:.,t-he first zgroup metal halide to bereduced is a solutionaofdower. chloride of said metal.

3. The ,process defined in claim 1, inwhich the solution of a second group metalv is a separately produced 1- cathode-product ofan electrolysis, under at atmosphere devoid of oxidizing gases, sofa substantially oxygen-free halide of theg-roupconsisting of. chloride, bromide, and iodide of a metal, ofthe, said second group.

4. .In the process. defined -,in claim 1, thestep of separately producing a single phase-cathode product adapted foruse as said-solution of second group. metal which comprises-electrolyzing an electrolyte initially consisting of a substantially i-OXYgen-free melt of at least one halide of a-psecond; group metalof the group consisting of chloride, bromide, and iodide,.using a chemically inert cathode:and.-an atmosphere devoid of oxidizing gases.

5. Process .of producing in subdivided form titanium from its halide, :which comprises preparing a substantially oxygen-free solution of said titanium halide in substantially oxygen-free molten sodium chloride, separately preparing .a substantially oxygen-free solution of a metal selected from the group consisting of the alkali metals and calcium in a melt of sodium chloride, and then etfectinga-reaction between said solutions exclusively by bringingsaid solutions together. in an environment free from .oxidizinggases and under such conditions that in thezzone ofv reaction there is no excess of either reactant over thestoichiometric equivalent for reaction .to form said titanium metal.

References Cited inithe file of this patent UNITED'STATES PATENTS 2,618,549 Glasser et.a.l.. Nov. 18, 1952 

1. PROCESS OF PRODUCING IN SUBDIVIDED FORM A FIRST GROUP METAL SELECTED FROM THE GROUP CONSISTING OF TI AND ZR FROM A HALIDE OF SAID FIRST GROUP METAL, WHICH COMPRISES PREPARING A SUBSTANTIALLY OXYGEN-FREE SOLUTION OF SAID FIRST GROUP METAL HALIDE IN A SUBSTANTIALLY OXYGENFREE MOLTEN HALIDE SELECTED FROM THE GROUP CONSISTING OF TH CHLORIDE, BROMIDE AND IODIDE OF A SECOND GROUP METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS, SEPARATELY PREPARING A SUBSTANTIALLY OXYGEN-FREE SOLUTION OF SAID SECOND GROUP METAL IN A MELT CONSISTING ESSENTIALLY OF AT LEAST ONE HALIDE SELECTED FROM THE GROUP CONSISTING OF THE CHLORIDE, BROMIDE AND IODIDE OF SAID SECOND GROUP METAL, AND THEN EFFECTING A REACTION BETWEEN SAID SOLUTIONS EXCLUSIVELY BY BRINGING SAID SOLUTIONS TOGETHER IN AN ENVIRONMENT FREE FROM OXIDIZING GASES AND UNDER SUCH CONDITIONS THAT IN THE ZONE OF REACTION THERE IS NO EXCESS OF EITHER REACTANT OVER THE STOICHIOMETRIC EQUIVALENT FOR REACTION TO FORM SAID FIRST GROUP METAL. 